TY - JOUR A1 - Schmaelzlin, Elmar A1 - Moralejo, Benito A1 - Rutowska, Monika A1 - Monreal-Ibero, Ana A1 - Sandin, Christer A1 - Tarcea, Nicolae A1 - Popp, Juergen A1 - Roth, Martin M. T1 - Raman imaging with a fiber-coupled multichannel spectrograph JF - Sensors N2 - Until now, spatially resolved Raman Spectroscopy has required to scan a sample under investigation in a time-consuming step-by-step procedure. Here, we present a technique that allows the capture of an entire Raman image with only one single exposure. The Raman scattering arising from the sample was collected with a fiber-coupled high-performance astronomy spectrograph. The probe head consisting of an array of 20 x 20 multimode fibers was linked to the camera port of a microscope. To demonstrate the high potential of this new concept, Raman images of reference samples were recorded. Entire chemical maps were received without the need for a scanning procedure. KW - multichannel Raman spectroscopy KW - astronomy spectrograph KW - optical fiber bundle KW - Raman imaging Y1 - 2014 U6 - https://doi.org/10.3390/s141121968 SN - 1424-8220 VL - 14 IS - 11 SP - 21968 EP - 21980 PB - MDPI CY - Basel ER - TY - JOUR A1 - Palyulin, Vladimir V. A1 - Ala-Nissila, Tapio A1 - Metzler, Ralf ED - Metzler, Ralf T1 - Polymer translocation: the first two decades and the recent diversification JF - Soft matter N2 - Probably no other field of statistical physics at the borderline of soft matter and biological physics has caused such a flurry of papers as polymer translocation since the 1994 landmark paper by Bezrukov, Vodyanoy, and Parsegian and the study of Kasianowicz in 1996. Experiments, simulations, and theoretical approaches are still contributing novel insights to date, while no universal consensus on the statistical understanding of polymer translocation has been reached. We here collect the published results, in particular, the famous–infamous debate on the scaling exponents governing the translocation process. We put these results into perspective and discuss where the field is going. In particular, we argue that the phenomenon of polymer translocation is non-universal and highly sensitive to the exact specifications of the models and experiments used towards its analysis. KW - solid-state nanopores KW - single-stranded-dna KW - posttranslational protein translocation KW - anomalous diffusion KW - monte-carlo KW - structured polynucleotides KW - dynamics simulation KW - equation approach KW - osmotic-pressure KW - membrane channel Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76266 SN - 1744-683X VL - 45 IS - 10 SP - 9016 EP - 9037 PB - the Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Jeon, Jae-Hyung A1 - Chechkin, Aleksei V. A1 - Metzler, Ralf T1 - Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion JF - Physical chemistry, chemical physics : PCCP N2 - Anomalous diffusion is frequently described by scaled Brownian motion (SBM){,} a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is ?x2(t)? [similar{,} equals] 2K(t)t with K(t) [similar{,} equals] t[small alpha]-1 for 0 < [small alpha] < 2. SBM may provide a seemingly adequate description in the case of unbounded diffusion{,} for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely{,} we demonstrate that under confinement{,} the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments{,} in particular{,} under confinement inside cellular compartments or when optical tweezers tracking methods are used. KW - single-particle tracking KW - living cells KW - random-walks KW - subdiffusion KW - dynamics KW - nonergodicity KW - coefficients KW - transport KW - membrane KW - behavior Y1 - 2014 U6 - https://doi.org/10.1039/C4CP02019G VL - 30 IS - 16 SP - 15811 EP - 15817 PB - The Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Zhao, Qiang A1 - Dunlop, John William Chapman A1 - Qiu, Xunlin A1 - Huang, Feihe A1 - Zhang, Zibin A1 - Heyda, Jan A1 - Dzubiella, Joachim A1 - Antonietti, Markus A1 - Yuan, Jiayin T1 - An instant multi-responsive porous polymer actuator driven by solvent molecule sorption JF - Nature Communications N2 - Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24 kPa, 20 degrees C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200 degrees C, 24 h) and pressing-pressure (100 MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn 'inert' objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials. Y1 - 2014 U6 - https://doi.org/10.1038/ncomms5293 SN - 2041-1723 VL - 5 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Zhang, Xiaoqing A1 - Zhang, Xinwu A1 - You, Qiong A1 - Sessler, Gerhard M. T1 - Low- cost, large- area, stretchable piezoelectric films based on irradiation- crosslinked poly ( propylene) JF - Macromolecular materials and engineering N2 - Low cost, large area, lightweight, stretchable piezoelectric films, based on space-charge electret with a foam structure (i.e., ferroelectrets or piezoelectrets), have been fabricated by using commercially available irradiation cross-linked poly(propylene) (IXPP) foam sheets. Piezoelectric d(33) coefficients are as high as 100pCN(-1). The piezoelectric performance in such IXPP films is well preserved for repeated strains of less than 10%. Piezoelectric d(33) coefficients are frequency independent in the range from 2 to 100Hz. Such new class materials may be applied in sensory skins, smart clothing, bio-inspired systems, microenergy harvesters, and so on. KW - crosslinked poly(propylene) KW - ferroelectret KW - piezoelectricity KW - stretchability Y1 - 2014 U6 - https://doi.org/10.1002/mame.201300161 SN - 1438-7492 SN - 1439-2054 VL - 299 IS - 3 SP - 290 EP - 295 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kurfuerst, P. A1 - Feldmeier, Achim A1 - Krticka, Jiri T1 - Time-dependent modeling of extended thin decretion disks of critically rotating stars JF - Astronomy and astrophysics : an international weekly journal N2 - Context. During their evolution massive stars can reach the phase of critical rotation when a further increase in rotational speed is no longer possible. Direct centrifugal ejection from a critically or near-critically rotating surface forms a gaseous equatorial decretion disk. Anomalous viscosity provides the efficient mechanism for transporting the angular momentum outwards. The outer part of the disk can extend up to a very large distance from the parent star. Aims. We study the evolution of density, radial and azimuthal velocity, and angular momentum loss rate of equatorial decretion disks out to very distant regions. We investigate how the physical characteristics of the disk depend on the distribution of temperature and viscosity. Methods. We calculated stationary models using the Newton-Raphson method. For time-dependent hydrodynamic modeling we developed the numerical code based on an explicit finite difference scheme on an Eulerian grid including full Navier-Stokes shear viscosity. Results. The sonic point distance and the maximum angular momentum loss rate strongly depend on the temperature profile and are almost independent of viscosity. The rotational velocity at large radii rapidly drops accordingly to temperature and viscosity distribution. The total amount of disk mass and the disk angular momentum increase with decreasing temperature and viscosity. Conclusions. The time-dependent one-dimensional models basically confirm the results obtained in the stationary models as well as the assumptions of the analytical approximations. Including full Navier-Stokes viscosity we systematically avoid the rotational velocity sign change at large radii. The unphysical drop of the rotational velocity and angular momentum loss at large radii (present in some models) can be avoided in the models with decreasing temperature and viscosity. KW - stars: mass-loss KW - stars: evolution KW - stars: rotation KW - hydrodynamics Y1 - 2014 U6 - https://doi.org/10.1051/0004-6361/201424272 SN - 0004-6361 SN - 1432-0746 VL - 569 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Haakh, Harald R. A1 - Henkel, Carsten A1 - Spagnolo, Salvatore A1 - Rizzuto, Lucia A1 - Passante, Roberto T1 - Dynamical Casimir-Polder interaction between an atom and surface plasmons JF - Physical review : A, Atomic, molecular, and optical physics N2 - We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze, in particular, how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relation of surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail. Y1 - 2014 U6 - https://doi.org/10.1103/PhysRevA.89.022509 SN - 1050-2947 SN - 1094-1622 VL - 89 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Mkrtchian, Vanik E. A1 - Henkel, Carsten T1 - On non-equilibrium photon distributions in the Casimir effect JF - Annalen der Physik N2 - The electromagnetic field in a typical geometry of the Casimir effect is described in the Schwinger-Keldysh formalism. The main result is the photon distribution function (Keldysh Green function) in any stationary state of the field. A two-plate geometry with a sliding interface in local equilibrium is studied in detail, and full agreement with the results of Rytov fluctuation electrodynamics is found. KW - Casimir effect KW - van der Waals interaction KW - quantum friction KW - nonequilibrium electrodynamics of nanosystems Y1 - 2014 U6 - https://doi.org/10.1002/andp.201300135 SN - 0003-3804 SN - 1521-3889 VL - 526 IS - 1-2 SP - 87 EP - 101 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Joulain, Karl A1 - Ben-Abdallah, Philippe A1 - Chapuis, Pierre-Olivier A1 - De Wilde, Y. A1 - Babuty, A. A1 - Henkel, Carsten T1 - Strong tip-sample coupling in thermal radiation scanning tunneling microscopy JF - Journal of quantitative spectroscopy & radiative transfer KW - Near-field thermal radiation KW - Infrared radiation KW - Local density of states KW - Scanning near-field optical microscopy KW - Tip-sample interactions KW - Local spectroscopy Y1 - 2014 U6 - https://doi.org/10.1016/j.jqsrt.2013.12.006 SN - 0022-4073 SN - 1879-1352 VL - 136 SP - 1 EP - 15 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Miedema, P. S. A1 - Beye, Martin A1 - Koennecke, R. A1 - Schiwietz, G. A1 - Föhlisch, Alexander T1 - The angular- and crystal-momentum transfer through electron-phonon coupling in silicon and silicon-carbide: similarities and differences JF - New journal of physics : the open-access journal for physics N2 - Electron-phonon scattering has been studied for silicon carbide (6H-SiC) with resonant inelastic x-ray scattering at the silicon 2p edge. The observed electron-phonon scattering yields a crystal momentum transfer rate per average phonon in 6H-SiC of 1.8 fs(-1) while it is 0.2 fs(-1) in crystalline silicon. The angular momentum transfer rate per average phonon for 6H-SiC is 0.1 fs(-1), which is much higher than 0.0035 fs(-1) obtained for crystalline silicon in a previous study. The higher electron-phonon scattering rates in 6H-SiC are a result of the larger electron localization at the silicon atoms in 6H-SiC as compared to crystalline silicon. While delocalized valence electrons can screen effectively (part of) the electron-phonon interaction, this effect is suppressed for 6H-SiC in comparison to crystalline silicon. Smaller contributions to the difference in electron-phonon scattering rates between 6H-SiC and silicon arise from the lower atomic mass of carbon versus silicon and the difference in local symmetry. KW - electron-phonon scattering KW - 6H-SiC KW - RIXS Y1 - 2014 U6 - https://doi.org/10.1088/1367-2630/16/9/093056 SN - 1367-2630 VL - 16 PB - IOP Publ. Ltd. CY - Bristol ER -